NVH performances determining driving comfort, which is one of feelings experienced by occupants when an automobile is in service, have been the focus of intense interest lately in automobile markets. However, selection of automobile materials is restricted by environmental problems. Accordingly, there is a need to develop materials being free from environmental problems as well as exhibiting improved NVH performances.
The term “NVH” used in the present invention is an acronym composed of the initial letters of three factors, i.e. “Noise”, “Vibration” and “Harshness” that affect car occupants' driving comfort. Thus, NVH components cover all automobile components that reduce the level of three factors and thus enable car occupants to feel optimal driving comfort. These three factors are defined as follows:
(1) Noise: an unpleasant sound externally or internally caused by a driving automobile
(2) Vibration: a phenomenon in which a driving automobile is vibrated at each cycle
(3) Harshness: a vibration or noise caused by impacts on road surfaces while driving on uneven roads
NVH components used for vehicles such as automobiles are currently molded by pressing a sound-absorbing heat-insulating material into a mould using a heat- or cold-press. As the material, there may be generally used an EVR sheet, urethane foam, glass wool, resin felt, polyester and the like. In particular, since a high-heat component such as an engine room is required to exhibit fire retardancy to some extent, it is made of glass wool. However, glass wool causes environmental pollutions associated with dust-scattering and waste disposal and is thus limited on its usage.
Polyester is harmless to humans and generates no dust by abrasion, thus being environmentally friendly. In addition, polyester has advantages of excellent heat-insulating property and superior sound-absorbing property. However, polyester has drawbacks of poor fire retardancy and unstability in shape due to high resilience during and after molding.
In this case, it is necessary to use a plasticizer so as to stably retain the shape of final products. Plasticizers currently used to retain the shape have problems in that they contain lead, hexavalent chrome (Cr), diisophthalate (DOP), PVC, a phenol resin, an urea resin, or P.P., all of which are regulated as toxic materials, or emit a toxic gas during ignition.